Face seal with insert

ABSTRACT

A method of determining wear of a seal element includes rotating a seal plate relative to the seal element and such that the seal plate and the seal element form a rotational sealing interface. The seal element includes an insert embedded in the seal element. A portion of the seal element is worn with a sealing face of the seal plate. The insert is contacted with the sealing face of the seal plate. A portion of the insert is worn to create a wear particle of the insert. The presence of the wear particle in a lubrication oil is sensed with an oil monitoring system.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of U.S. application Ser. No. 16/373,165filed Apr. 2, 2019 for “Face Seal with Insert” by C. Guo, Z. Chaudhry,and N. Shuaib.

BACKGROUND

The present disclosure relates to seal assemblies. More particularly,the present disclosure relates to multi-material carbon face seals.

In existing bearing assemblies for aircraft bearing compartments, a dryface seal often provides a critical sealing interface within the bearingcompartment. If the dry face seal loses its sealing capability, oil andmist within the compartment can leak into the bleed air. It isbeneficial to have a dry seal configuration that provides a fully sealedinterface at all times.

Occasionally, it is possible for a dry face seal to lose its sealingcapability due to excessive wear of the seal. In some instances,metal-to-metal contact and wear of seal carriers and seal plates cangenerate metal particles as well as sparks due to frictional heatingwhich may ignite lubrication oil in the compartment.

SUMMARY

A method of determining wear of a seal element includes rotating a sealplate relative to the seal element and such that the seal plate and theseal element form a rotational sealing interface. The seal elementincludes an insert embedded in the seal element. A portion of the sealelement is worn with a sealing face of the seal plate. The insert iscontacted with the sealing face of the seal plate. A portion of theinsert is worn to create a wear particle of the insert. The presence ofthe wear particle in a lubrication oil is sensed with an oil monitoringsystem.

A seal assembly for a bearing compartment of a turbine engine includes aseal plate, a seal carrier, a seal element, and an insert. The sealplate includes a first sealing face on a first axial end of the sealplate. The seal carrier is disposed axially from and coaxially with theseal plate. The seal element extends annularly and includes a secondsealing face on a first axial end of the seal element. The seal carrieris in contact with the seal element and holds the seal element in placeagainst the seal plate such that the first sealing face of the sealplate and the second sealing face of the seal element form a sealinginterface. The insert is disposed in the seal element such that theinsert is embedded in the seal element at a predetermined distance fromthe second sealing face.

The present summary is provided only by way of example, and notlimitation. Other aspects of the present disclosure will be appreciatedin view of the entirety of the present disclosure, including the entiretext, claims, and accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a quarter section view of a gas turbine engine.

FIG. 2A is an enlarged cross-section view of portion 2-2 in FIG. 1illustrating a seal assembly in a first, un-worn state.

FIG. 2B is an enlarged cross-section view of portion 2-2 in FIG. 1illustrating a seal assembly in a second, worn state with a seal plateinto contact with an insert of the seal element.

FIG. 3 is a simplified schematic view of an oil debris monitoring systemthat is connected to a bearing compartment of the gas turbine engine.

While the above-identified figures set forth one or more embodiments ofthe present disclosure, other embodiments are also contemplated, asnoted in the discussion. In all cases, this disclosure presents theinvention by way of representation and not limitation. It should beunderstood that numerous other modifications and embodiments can bedevised by those skilled in the art, which fall within the scope andspirit of the principles of the invention. The figures may not be drawnto scale, and applications and embodiments of the present invention mayinclude features and components not specifically shown in the drawings.

DETAILED DESCRIPTION

A seal assembly can be modified such that the seal carrier of the sealassembly comes into gradual and gentle contact with the seal plate justbefore the seal is fully worn out. In this arrangement, metal-to-mentalcontact between the seal carrier and the seal plate can generateparticles of ablated metal that displace into lubricating oil. When anoil monitoring system picks up any traces of metal in the oil, it willalert the engine monitoring module about the seal condition. A concernof this modification is associated with the metal-to-metal rub (slide),as sparks could, under some circumstances, be generated due to themetal-to-metal rubbing of the seal plate and the seal carrier. There canalso be a concern with respect to whether the sparks generated will besevere enough to ignite the lubrication oil.

A carbon seal is disclosed herein that includes an insert embedded inthe carbon seal at a set depth, such that when wear of the carbon sealreaches that pre-determined depth, wear particles of the insert will bedisposed into the lubrication oil and the oil monitoring system willalert the engine control/pilot about the status of the seal.

FIG. 1 shows a side elevation cutaway view of gas turbine engine 10 andincludes axial centerline 12, upstream airflow inlet 14, downstreamairflow exhaust 16, fan section 18, compressor section 20 (with lowpressure compressor (“LPC”) section 20A and high pressure compressor(“HPC”) section 20B), combustor section 22, turbine section 24 (withhigh pressure turbine (“HPT”) section 24A and low pressure turbine(“LPT”) section 24B), engine housing 26 (with inner case 28 (e.g., acore case) and outer case 30 (e.g., a fan case)), fan rotor 32, LPCrotor 34, HPC rotor 36, HPT rotor 38, LPT rotor 40, gear train 42, fanshaft 44, low speed shaft 46, high speed shaft 48, bearing compartments50A, 50B, and 50C, plurality of bearings 52, core gas path 54, bypassgas path 56, combustion chamber 58, combustor 60, and oil debris monitor62 (“ODM 62”).

Gas turbine engine 10 extends along axial centerline 12 between upstreamairflow inlet 14 and downstream airflow exhaust 16. Gas turbine engine10 includes fan section 18, compressor section 20, combustor section 22,and turbine section 24. Compressor section 20 includes LPC section 20Aand HPC section 20B. Turbine section 24 includes HPT section 24A and LPTsection 24B.

Fan section 18, compressor section 20, combustor section 22, and turbinesection 24 are arranged sequentially along centerline 12 within enginehousing 26. Engine housing 26 includes inner case 28 (e.g., a core case)and outer case 30 (e.g., a fan case). Inner case 28 may house one ormore of fan section 18, compressor 20, combustor section 22, and turbinesection 24 (e.g., an engine core). Outer case 30 may house at least fansection 18. Each of gas turbine engine sections 18, 20A, 20B, 24A and24B includes respective rotors 32-40. Each of these rotors 32-40includes a plurality of rotor blades arranged circumferentially aroundand connected to one or more respective rotor disks. The rotor blades,for example, may be formed integral with or mechanically fastened,welded, brazed, adhered and/or otherwise attached to the respectiverotor disk(s).

Fan rotor 32 is connected to gear train 42, for example, through fanshaft 44. Gear train 42 and LPC rotor 34 are connected to and driven byLPT rotor 40 through low speed shaft 46. The combination of at least LPCrotor 34, LPT rotor 40, and low speed shaft 46 may be referred to as “alow speed spool.” HPC rotor 36 is connected to and driven by HPT rotor38 through high speed shaft 48. The combination of at least HPC rotor36, HPT rotor 38, and high speed shaft 48 may be referred to as “a highspeed spool.” Shafts 44-48 are rotatably supported by a plurality ofbearings 52, which can be rolling element bearings, thrust bearings, orother types of bearings. Each of these bearings 52 is connected toengine housing 26 by at least one stationary structure such as, forexample, an annular support strut. ODM 62 is an oil monitoring systemconfigured to monitor the contents of lubrication oil. In thisnon-limiting embodiment, ODM 62 is fluidly connected to bearingcompartment 50B. In the illustrated example, ODM 62 is shownschematically as a simplified block. In this example, ODM 62 includes asensor that senses for the presence of particulates in lubrication oilwithin gas turbine engine 10.

During operation, air enters gas turbine engine 10 through airflow inlet14. Air is directed through fan section 18 and is then split into eithercore gas path 54 or bypass gas path 56. Core gas path 54 flowssequentially through fan section 18, compressor section 20, combustorsection 22, and turbine section 24. The air within core gas path 54 maybe referred to as “core air.” Bypass gas path 56 flows through a ductbetween inner case 28 and outer case 30. The air within bypass gas path56 may be referred to as “bypass air.”

The core air is compressed by LPC rotor 34 and HPC rotor 36 and directedinto combustion chamber 58 of combustor 60 in combustor section 22. Fuelis injected into combustion chamber 58 and mixed with the core air thathas been compressed by compressor section 20 to provide a fuel-airmixture. This fuel-air mixture is ignited and combustion productsthereof expand and flow through and sequentially cause HPT rotor 38 andLPT rotor 40 to rotate. The rotations of HPT rotor 38 and LPT rotor 40drive rotation of LPC rotor 34 and HPC rotor 36, respectively andcompression of the air received from core gas path 54. The rotation ofLPT rotor 40 also drives rotation of fan rotor 32, which propels bypassair through and out of bypass gas path 56. Also during operation, ODM 62monitors lubrication oil in order to sense the presence of wearparticles in the lubrication oil.

FIG. 2A is an enlarged cross-section view of portion 2-2 in FIG. 1illustrating seal assembly 64 in a first, un-worn state. FIG. 2A showsaxial centerline 12, seal assembly 64, seal plate 66 (with first axialend 68 and first sealing face 70), seal carrier 72 (with axial end-face74), seal element 76 (with first axial end 78, second sealing face 80,and hole 82), filler 84, sealing interface 86, insert 88 (with axialend-face 90), first distance D₁, and second distance D₂.

Seal plate 66 is a seal element for rotary applications. In thisembodiment, seal plate 66 is a seat for a seal. First axial end 68 is anaxial end of seal plate 66. First sealing face 70 is an end-wall or faceof seal plate 66. Seal carrier 72 is an annular containment ring ofsolid material. In this embodiment, seal carrier 72 includes a metallicmaterial. Axial end-face 74 is an axial end of seal carrier 72. Sealelement 76 is a face seal. In this embodiment, seal element 76 is acarbon dry face seal. First axial end 78 is an axial end of seal element76. Second sealing face 80 is an end-wall or face of seal element 76.Hole 82 is an opening or passage. In this example, hole 82 is formed viamachining or drilling into an axial end-face of seal element 76 that ison an opposite end of seal element 76 from first axial end 78. Filler 84is a solid substance. In this embodiment, filler 84 can be a solidifiedepoxy or other bonding material such as a polymer.

Sealing interface 86 is an interface between first sealing face 70 ofseal plate 66 and second sealing face 80 of seal element 76. Insert 88is a piece of solid material. In this non-limiting embodiment, insert 88is a plug in the shape of a cylinder. Also in this embodiment, amaterial of insert 88 includes a material with a low propensity forspark creation. For example, the material of insert 88 includes a lesserpropensity for spark creation than a material of seal carrier 72.Additionally, the material of insert 88 can include a particularferromagnetic or non-ferromagnetic material, such that the magnetism ofthe material of insert 88 is different that a magnetism of the materialof seal element 76. Axial end-face 90 is an end-wall or face of insert88. First distance D₁ is a distance between first sealing face 70 ofseal plate 66 and axial end-face 74 of seal carrier 72. Second distanceD₂ is a distance between first sealing face 70 of seal plate 66 andaxial end-face 90 of insert 88.

In this embodiment, seal assembly 64 is disposed in bearing compartment50B. Although seal assembly 64 is discussed as being disposed in bearingcompartment 50B, seal assembly 64 can be disposed in any one of bearingcompartments 50A, 50B, 50C, or another compartment of gas turbine engine10. In this embodiment, seal plate 66 can be disposed about one of fanshaft 44, low speed shaft 46, or high speed shaft 48 of gas turbineengine 10. First sealing face 70 at first axial end 68 of seal plate 66is in contact with second sealing face 80 at first axial end 78 of sealelement 76. Seal carrier 72 is disposed around and in contact with sealelement 76. Axial end-face 74 of seal carrier 72 is separated from firstsealing face 70 of seal plate 66 by first distance D₁.

Seal element 76 is fit within a portion of seal carrier 72 and is incontact with seal plate 66. Second sealing face 80 at first axial end 78is in sealing engagement with first sealing face 70 at first axial end68 of seal plate 66. Hole 82 is disposed in a portion of seal element76. In the illustrated example, hole 82 is oriented axially parallelrelative to axial centerline 12, to seal plate 66, to seal carrier 72,and to seal element 76. Filler 84 is disposed within a portion of hole82 that is not occupied by insert 88. Sealing interface 86 is located ata plane where first sealing face 70 of seal plate 66 and second sealingface 80 of seal element 76 are in contact.

In the illustrated embodiment, an axial depth of insert 88 extends onlya portion of the axial length of seal element 76. In other non-limitingembodiment, insert 88 can extendthe full axial length or a majority ofthe full axial length of seal element 76. Insert 88 is disposed withinhole 82. In the illustrated example, a single insert 88 is inserted in asingle hole 82. In other embodiments, seal element 76 can include morethan one hole 82 each with their own insert 88, and with the distancesbetween the multiple inserts 88 and seal plate 66 varying between thedifferent inserts 88. In this embodiment, axial end-face 90 of insert 88is separated from second distance D₂ from first sealing face 70 of sealplate 66. In this illustrated embodiment, first distance D₁ is greaterthan second distance D2 and second distance D₂ is greater than zero.

First sealing face 70 at first axial end 68 of seal plate 66 rotatesrelative to seal element 76 and forms sealing interface 86 with secondsealing face 80 at first axial end 78 of seal element 76. Seal carrier72 holds seal element 76 in place against seal plate 66. In thisexample, seal carrier 72 contains seal element 70 both radially andaxially. Second sealing face 80 at first axial end 78 of seal element 76provides a face seal for a rotating interface (e.g., sealing interface86). Hole 82 provides an opening in which insert 88 is mounted. Filler84 holds insert 88 in place within hole 82 and prevents insert 88 frommoving out of hole 82. Sealing interface 86 prevents transmission of afluid across sealing interface 86 during operation of engine 10.

As will be discussed with respect to FIG. 2B, insert 88 provides wearparticles characteristic to insert 88 in such a way that indicates thatseal element 76 has worn down an unacceptable amount. Axial end-face 90of insert 88 remains a positive distance from first sealing face 70 ofseal plate 66 until a portion of seal element 76 between insert 88 andseal plate 66 is worn down. In another example with multiple inserts 88disposed in sealing element 76, inserts 88 can be disposed at differentdistances from first sealing face 70 of seal plate 66 so as to provide astaging effect as between the release of wear particles of the variousinserts 88. Different materials can be selected between the variousmultiple inserts 88, such that ODM 62 can detect the presence of theindividual inserts 88 and differentiate between the different materialsof the different inserts 88. As such, different wear depths of sealelement 76 could be determined based on the sensed presence ofparticular material of the various inserts 88 in the lubrication oil.

When the wear of seal element 76 reaches the pre-determined depth (i.e.,the position of axial end-face 90 of insert 88), wear particles ofinsert 88 will be disposed into the lubrication oil. These wearparticles of insert 88 are then sensed by ODM 62 that monitors thelubrication oil for the presence of particulates. For example, ODM 62can monitor for and sense the presence of particles containing aparticular level of ferromagnetism (and/or non-ferromagnetism). Whenwear particles of insert 88 are sensed in the lubrication oil, ODM 62will provide a notification so as to alert engine control and/or thepilot about the status of seal assembly 64. The selection of thematerial of insert 88 will make sure that the material of insert 88 doesnot generate sparks in the event of seal plate 66 wearing against insert88. Insert 88 and its associated wear particles will be compatible withthe oil system management (e.g., no harm to the oil). The material ofinsert 88 is also sensitive for ODM 62 to pick up the presence of wearparticles of insert 88.

FIG. 2B is an enlarged cross-section view of portion 2-2 in FIG. 1illustrating seal assembly 64 in a second, worn state with seal plate 66into contact with insert 88 of seal element 76. FIG. 2 shows axialcenterline 12, seal assembly 64, seal plate 66 (with first axial end 68and first sealing face 70), seal carrier 72 (with axial end-face 74),seal element 76 (with first axial end 78, second sealing face 80, andhole 82), filler 84, sealing interface 86, insert 88 (with axialend-face 90), first distance Di, and second distance D₂.

In the illustrated embodiment, a first coefficient of friction betweenseal plate 66 and seal carrier 72 is less than a second coefficient offriction between seal plate 66 and insert 88. In the illustratedembodiment, seal element 76 has been worn down due to friction atsealing interface 86 between seal element 76 and seal plate 66. Forexample, in FIG. 2B second distance D₂ is shown as zero. Here, firstdistance D₁ is shown as having a value greater than zero such that axialend-face 74 of seal carrier 72 is out of contact with first sealing face70 of seal plate 66.

With the second coefficient of friction between seal plate 66 and insert88 being greater than the first coefficient of friction between sealplate 66 and seal carrier 72, friction caused by relative rotationalmovement between seal plate 66 and insert 88 causes an amount of wearparticles to be dislodged from insert 88 and dispersed into thelubrication oil of bearing compartment 50B.

For example, in one limiting embodiment, a method of determining wear ofseal element 76 can include the following. Seal plate 66 is rotatedrelative to seal element 76. A flow of lubrication oil is monitored withODM 62. A portion of seal element 76 is worn by first sealing face 70 ofseal plate 66. Insert 88 is contacted with first sealing face 70 of sealplate 66. A portion of insert 88 is worn to create a wear particle ofinsert 88. The presence of the wear particle of insert 88 in alubrication oil is sensed with ODM 62. In one example, sensing thepresence of the wear particle of insert 88 in the lubrication oilincludes scanning the lubrication oil with a sensor to detect thepresence of objects that are not the lubrication oil. In anotherexample, sensing the presence of the wear particle of insert 88 in thelubrication oil includes scanning the lubrication oil with the sensor todetect the presence of a particle including the same materialcomposition as a material of insert 88. Notification of the presence ofthe wear particle in the lubrication oil is provided by ODM 62.

Seal assembly 64 with insert 88 enables monitoring and detection of wearstages of seal element 76. For example, ODM 62 is able to detect whenseal plate 66 comes into contact with insert 88 by way of detecting wearparticles of insert 88 in the lubrication oil. The ability to detect thepresence of wear particles of insert 88 enables providing an alert thatseal element 76 has reached a threshold limit indicative of the stageprior to seal plate 66 coming into contact with seal carrier 72. Giventhis, incorporating insert 88 into seal element 76 allows for preventionof contact between seal plate 66 and seal carrier 72 thereby preventingwear debris from seal carrier 72 being emitted into the lubrication oiland also preventing formation of sparks caused by contact between sealplate 66 and seal carrier 72.

As such, bearing assembly 64 with insert 88 provides the benefit ofbetter reliability and earlier debris detection by ODM 62. Also, enginerepairs can be scheduled and planned ahead of time instead of waitingfor seal plate 66 to come into contact with seal carrier 72 and sealcarrier 72 being damaged. Additionally, bearing assembly 64 with insert88 avoids events of oil loss and fumes in the cabin that are consideredsafety risks to the operation of the aircraft.

FIG. 3 is a simplified schematic illustration of oil debris monitoringsystem 62 that is connected to bearing compartment 50B and shows sensor92, detector 94, first pump 96, filter 98, tank 100, and second pump102.

Sensor 92 is a device for sensing the presence of particulate inlubrication oil. Detector 94 is a device for detecting particulates inthe lubrication oil. First pump 96 and second pump 102 are devices forcreating pressure in the lubrication oil passing through ODM 62. Filter98 is a device for removing particulate from the flow of lubricationoil. Tank 100 is a container for temporarily storing an amount of thelubrication oil.

Bearing compartment 50B, sensor 92, detector 94, first pump 96, filter98, tank 100, and second pump 102 of ODM 62 are connected in a seriesflow arrangement as shown in FIG. 3. During operation of gas turbineengine 10, a flow of lubrication oil is drawn out of bearing compartment50B to ODM 62. Once the flow of lubrication oil enters ODM 62, the flowof lubrication oil passes sequentially to sensor 92, to detector 94, tofirst pump 96, to filter 98, to tank 100, to second pump 102, and thenback into bearing compartment 50B. In another example, any one or all ofsensor 92, detector 94, first pump 96, filter 98, tank 100, and/orsecond pump 102 of ODM 62 can be connected to a controller via wired orwireless communication.

For example, in one limiting embodiment, a method of determining wear ofseal element 76 can include the following. Seal plate 66 is rotatedrelative to seal element 76. A flow of lubrication oil is monitored withODM 62. A portion of seal element 76 is worn by first sealing face 70 ofseal plate 66. Insert 88 is contacted with first sealing face 70 of sealplate 66. A portion of insert 88 is worn to create a wear particle ofinsert 88. The presence of the wear particle of insert 88 in alubrication oil is sensed with ODM 62. In one example, sensing thepresence of the wear particle of insert 88 in the lubrication oilincludes scanning the lubrication oil with sensor 92 and/or detector 94to detect the presence of objects that are not the lubrication oil. Inanother example, sensing the presence of the wear particle of insert 88in the lubrication oil includes scanning the lubrication oil with sensor92 and/or detector 94 to detect the presence of a particle including thesame material composition as a material of insert 88. In onenon-limiting example, detecting the presence of a particle including thesame material composition as a material of insert 88 can includedetermining a magnetism of the particle and comparing that level ofmagnetism to the known magnetism of insert 88. Once the presence of awear particle of insert 88 in the lubrication oil is determined,notification of the presence of the wear particle in the lubrication oilis provided by ODM 62.

Discussion of Possible Embodiments

A method of determining wear of a seal element includes rotating a sealplate relative to the seal element and such that the seal plate and theseal element form a rotational sealing interface. The seal elementincludes an insert embedded in the seal element. A portion of the sealelement is worn with a sealing face of the seal plate. The insert iscontacted with the sealing face of the seal plate. A portion of theinsert is worn to create a wear particle of the insert. The presence ofthe wear particle in a lubrication oil is sensed with an oil monitoringsystem.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingsteps, features, configurations and/or additional components.

A flow of the lubrication oil can be monitored with the oil monitoringsystem.

Notification of the presence of the wear particle in the lubrication oilcan be provided with the oil monitoring system.

The lubrication oil can be scanned with a sensor to detect the presenceof objects that are not the lubrication oil.

The lubrication oil can be scanned with the sensor to detect thepresence of a particle including the same material composition as amaterial of the insert.

A seal assembly can be modified such that the seal carrier of the sealassembly comes into gradual and gentle contact with the seal plate justbefore the seal is fully worn out. In this arrangement, metal-to-mentalcontact between the seal carrier and the seal plate can generateparticles of ablated metal that displace into lubricating oil. When anoil monitoring system picks up any traces of metal in the oil, it willalert the engine monitoring module about the seal condition. A concernof this modification is associated with the metal-to-metal rub (slide),as sparks could, under some circumstances, be generated due to themetal-to-metal rubbing of the seal plate and the seal carrier. There canalso be a concern with respect to whether the sparks generated will besevere enough to ignite the lubrication oil.

The assembly of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components.

A first coefficient of friction between the seal plate and the sealcarrier can be less than a second coefficient of friction between theseal plate and the insert.

The insert can comprise a material with a lesser propensity for sparkcreation than a material of the seal carrier.

The seal element can comprises a hole extending axially through aportion of the seal element, wherein the insert can be disposed in thehole.

A remaining portion of the hole can comprise a filler material that canhold the insert in a fixed position in the hole.

The seal carrier can include an axial end-face that faces towards and/orthat is disposed a first distance from the first sealing face of theseal plate, wherein the insert can include an axial end-face that facestowards and/or that is disposed a second distance from the first sealingface of the seal plate, wherein the second distance can be less than thefirst distance.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. A method of determining wear of a seal element, the methodcomprising: rotating a seal plate relative to the seal element, whereinthe seal plate and the seal element form a rotational sealing interface,wherein the seal element includes an insert embedded in the sealelement; wearing a portion of the seal element with a sealing face ofthe seal plate; contacting the insert with the sealing face of the sealplate; wearing a portion of the insert to create a wear particle of theinsert; and sensing the presence of the wear particle in a lubricationoil with an oil monitoring system.
 2. The method of claim 1, furthercomprising monitoring a flow of the lubrication oil with the oilmonitoring system.
 3. The method of claim 2, further comprisingproviding notification of the presence of the wear particle in thelubrication oil with the oil monitoring system.
 4. The method of claim1, wherein sensing the presence of the wear particle in the lubricationoil comprises scanning the lubrication oil with a sensor to detect thepresence of objects that are not the lubrication oil.
 5. The method ofclaim 4, wherein sensing the presence of the wear particle in thelubrication oil comprises scanning the lubrication oil with the sensorto detect the presence of a particle including the same materialcomposition as a material of the insert.
 6. The method of claim 5 andfurther comprising: determining a magnetism of the particle andcomparing the magnetism of the particle to a known magnetism of thematerial of the insert.